On the last full day of President Donald Trump's presidency and on the eve of Joe Biden's inauguration, deaths from COVID-19 in the United States topped 400,000.

The death toll of 400,022 also comes as February approaches, the month of the first reported deaths from COVID-19 in the US, as the pandemic continues to rage across the nation.

Biden's incoming White House chief of staff, Ron Klain, noted the grave loss of life and the pandemic that Biden will inherit when he is sworn in on Wednesday, saying that he has tried to prepare the country for "a very, very, very dark winter".

The US reached the 400,000 milestone in just under a year. The first known deaths from the virus in the US were in early February 2020, both in Santa Clara County in California.

More than 100,000 Americans who had coronavirus have died in the past five weeks. It took more than 16 weeks for the US to reach 100,000 deaths, but less than five weeks to go from 300,000 to 400,000.

"It's very hard to wrap your mind around a number that is so large, particularly when we've had 10 months of large numbers assaulting our senses and really, really horrific images coming out of our hospitals and our morgues," Kirsten Bibbins-Domingo, chair of epidemiology at the University of California, San Francisco, told National Public Radio on Tuesday.

The US death toll is the world's highest, even though the country has less than 5 percent of the world's population. The number of deaths so far is nearly equal to the number of Americans killed in World War II, around 405,000, according to the Veterans Affairs Department.

More than 2 million people have been recorded killed by the virus worldwide, according to data from the Johns Hopkins University Coronavirus Resource Center.

A forecast by the Centers for Disease Control and Prevention (CDC) predicts that the US death toll could be 477,000 by Feb 6.

A widely cited model by the University of Washington projects the death toll will reach nearly 567,000 by May 1.

The US coronavirus fatalities have accelerated through the fall into the winter, reaching a record level in January. During some weeks of January, the average number of deaths per day exceeded 3,300, more than the number of people killed in the Sept 11 terrorist attacks.

Total cases of the coronavirus in the US have surpassed 24 million.

The single deadliest day in the US amid the pandemic was Jan 12 — more than 4,400 deaths were reported.

Unlike the early days of the pandemic in the US when the disease was centered in a handful of big, mostly Northeastern cities, the current surge is widespread.

California, New York, Texas and Florida have reported the largest number of new cases in the past week.

California currently has the most cases, with 28,027. On Tuesday, it became the first state to reach 3 million cases. Roughly 1 out of every 13 people in the state have been infected at some point during the pandemic.

A second new coronavirus variant has been found in the state. Different from a highly contagious variant first identified in the UK, the variant in California is popping up more frequently across the state.

The state's public health department said Sunday that it isn't yet clear whether the variant is highly contagious or is just being identified frequently as lab work becomes more sophisticated.

Vaccines being given to millions of Americans now hold the potential to halt the coronavirus, but the vaccination deployment has been bumpy. As of Jan 14, more than 31 million doses of two available vaccines have been distributed in the US, but only 12 million people have been vaccinated, according to the CDC.

Biden has promised to vaccinate 100 million people in his first 100 days in office, a goal Dr Anthony Fauci, the nation's top infectious diseases expert, told NBC on Sunday was "absolutely a doable thing".